Can I choose to renew the COE of my car anytime or can it be done only when it is nearing expiry?

Renewing your COE is preferable when the cost of the PQP is at best. To renew the COE months (or even more earlier) before reaching the expiry, the current balance of COE will be forfeited and you are no longer eligible for the PARF rebate. With that, ensure the PQP price you're getting is worth the amount of COE you're forfeiting.